Chapter

Interactive Multimedia and Next Generation Networks

Volume 3311 of the series Lecture Notes in Computer Science pp 25-36

Adaptive VoIP Transmission over Heterogeneous Wired/Wireless Networks

  • Abdelbasset TradAffiliated withINRIA, Planete Project
  • , Qiang NiAffiliated withINRIA, Planete Project
  • , Hossam AfifiAffiliated withINT-INRIA

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Abstract

In this paper, we present an adaptive architecture for the transport of VoIP traffic over heterogeneous wired/wireless Internet environments. This architecture uses a VoIP gateway associated with an 802.11e QoS enhanced access point (QAP) to transcode voice flows before their transmissions over the wireless channel. The instantaneous bit rate is determined by a control mechanism based on the estimation of channel congestion state. Our mechanism dynamically adapts audio codec bit rate using a congestion avoidance technique so as to preserve acceptable levels of quality. A case study presenting the results relative to an adaptive system transmitting at bit rates typical of G.711 PCM (64 kbit/s) and G.726 ADPCM (40, 32, 24 and 16 kbit/s) speech coding standards illustrates the performance of the proposed framework. We perform extensive simulations to compare the performance between our adaptive audio rate control and TFRC mechanism. The results show that the proposed mechanism achieves better voice transmission performance, especially when the number of stations is fairly large.